Drive systems for passenger transit type vehicle doors must meet a number of conflicting requirements, as is generally well known in the passenger transit industry. For example, these doors must open and close rather quickly and smoothly upon receipt of a control signal to open or close. Additionally, these doors must have a positive lock to prevent them from being inadvertently opened when the transit vehicle is in motion. On the other hand, such doors require a manual release to unlock and open them in the event of an emergency.